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Keeping the internal environment of the body in
a Steady state (relatively constant) condition,despite changes in the external environment.
It is controlled by feedback mechanisms -cycle ofevents in which the status of a body condition is
continually monitored, evaluated, changed, re-
monitored, re-evaluated, etc.
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metabolic reactions are controlledby enzymes
enzymes work best in a narrow
range of temperature & pH only important to keep internal
environment as steady as possible
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Negative feedback mechanisms (used bymost of the body's systems) are callednegative because the information caused bythe feedback causes a reverse of the
response.
Positive feedback mechanism is used in somecases. Input increases or accelerates the
response.
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Negative feedback occurs in a biochemicalpathway where the products of the reactioninhibit production of the substance/enzymethat controlled their formation.
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Rise above
normal value
Fall below
normal value
normal
value
Corrective
Mechanism
Corrective
Mechanism
NEGATIVEFEEDBACK
MECHANISM
normal
value
negative
feedback
negative
feedback
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It occurs when the accumulation of theproduct stimulates production of anenzyme/hormone responsible for thatproduct's production.
In other words, information produced by thefeedback increases and accelerates theresponse.
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Kidneys: regulate water &mineral salts concentration
Skin: regulate body
temperature Liver & Pancreas: regulate
blood glucose level
Blood vessel: coagulation
Womb: Parturition
kidney
liver
pancreas+
skin
tissue
cells
blood
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Regulate water potential inTissue Fluid
Organ involved: KIDNEYS
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Normal Water
Content in Blood
After Sweating
Concentrated
Blood
Largerproportion of
water is
reabsorbed
ConcentratedUrine is
produced
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Normal Water
Content in Blood
After Drinking
Diluted Blood
Smallerproportion of
water is
reabsorbed
Diluted Urineis produced
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After having a very salty meal
produce concentrated urine to removeexcess salts in solution form
extra water is needed to be excreted along
with the excess salts
sensation of thirst (drink more water to
compensate for the water loss)
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controlled by Negative feedbackmechanism
controlled by insulin secreted from
the islets of Langerhans in pancreas Diabetes - malfunction of pancreas
(does not secrete enough insulin)
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Liverconverts
glycogen to
glucose
normal blood
glucose level
Blood glucose
level fallsSoonafter a
meal
Longafter a
meal Blood glucose
level rises
normal blood
glucose level
Too
High
Too
Low
Pancreas
secretes
insulin
Pancreas
secretes lessinsulin
Livercoverts
glucose to
glycogen
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FIN ^_^